Pneumatic signal responsive hydraulically actuated positioners for high pressure servo-valves provided with a compensating or followup mechanism



Feb. 19, 1957 R s, w s 2,781,744

PNEUMATIC SIGNAL RESPONSIVE HYDRAULICALLY ACTUATED POSITIONERS FOR HIGH PRESSURE SERVO-VALVES PROVIDED WITH A COMPENSATING OR FOLLOWUP MECHANISM 4 Sheets-Sheet l IN VEN TOR. AAY 5. W/u/A/ws Filed Sept. 2, 1954 Feb. 19, 1957 R s, w s 2,781,744

PNEUMATIC SIGNAL RESPONSIVE HYDRAULICALLY ACTUATED POSITIONERS FOR HIGH PRESSURE SERVO-VALVES PROVIDED WITH A COMPENSATING OR FOLLOWUP MECHANISM Filed Sept. 2, 1954 4 Sheets-Sheet 2 INVENTOR. RAY 5. I V/AA/AMS 1957 R. s. WILLIAMS PNEUMATIC SIGNAL RESPONSIVE HYDRAULICALLY ACTUATED POSITIONERS FOR HIGH PRESSURE SERVO-VALVES PROVIDED WITH A COMPENSATING OR FOLLOWUP MECHANISM 4 Shets-Sheet 5 Filed Sept. 2, 1954 INVEN TOR. R Y 5. VV/LZ/AMS United States Patent PNEUMATIC SIGNAL RESPONSIVE HYDRAULI- CALLY ACTUATED POSITIONERS FOR HIGH PRESSURE SERVO-VALVES PROVIDED WITH A COMPENSATING OR FOLLOWUP MECHANISM Ray S. Williams, Orrville, Ohio, assignor to Hogan Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Application September 2, 1954, Serial No. 453,825

9 Claims. (Cl. 121-41) This invention relates to pneumatic signal responsive hydraulically actuated positioners for high pressure servovalves provided with a compensating or followup mechanism which is coupled to the positioner, and the servovalve. The compensating or followup mechanism is actuated by a movable member of a controlled device such as an hydraulic power cylinder. The invention is so arranged and constructed that it may be assembled as a compact self-contained unit and applied to very large power cylinders that operate on very large devices such as valves, but which can be located in a position apart from the hydraulic cylinder.

Heretofore, power cylinders have been provided with pilot valves and followups or compensating bars that returned the pilot valve to neutral position when the piston had moved a predetermined portion of its stroke, depending upon the extent to which the pilot valve had been opened. Power cylinders of that type are illustrated by United States Patent No. 2,044,936. Such power cylinders are quite small so that the pilot valve and compensating bar and the valve shut-off cam may be conveniently mounted on the power cylinder.

However, where extremely large valves are to be operated by very large power cylinders, the hydraulic fluid pressure may be of the order of 1500 to 2000 p. s. i. Such cylinders have a large diameter and a long stroke. For that reason, it is not practical to mount the servo-valve, its operating mechanism and the compensating mechanism on the power cylinder because the compensating mechanism in such a case would be too large and cumbersome to be practical.

An object of this invention is to provide a servo-valve for supplying a high pressure fluid such as oil to a large high pressure power cylinder, a signal controlled positioner for operating the servo-valve, and a compensating mechanism for operating the servo-valve to neutral position in response to motion of the piston of the power cylinder, all of which mechanism may be mounted apart from the power cylinder.

A further object of the invention is to provide the above identified servo-valve and its associated mechanism as a self-contained unit which may be mounted in a convenient and accessible location with reference to the power cylinder and connected to it by a relatively simple transmission linkage.

A further object of the invention is to provide an hydraulic positioner of the piston type that operates in response to a pneumatic signal to actuate the servo-valve, and which includes a compensating mechanism, the latter being operated by motion of a piston or other controlled movable member to set the servo-valve in neutral position unless the input signal requires the servo-valve to remain out of neutral position until the movable member has reached the point required by the signal pressure.

The above and other objects of the invention will be apparent to those of ordinary skill in the art to which the invention pertains from the following specification and the drawings.

2,781,744 Patented Feb. 19, 1957 ICE In the drawings:

Figure 1 is a more or less schematic view of a power cylinder of the hydraulic type and a pneumatic signal controlled hydraulic positioner and an hydraulic servo-valve for controlling operation of the cylinder, the mechanism being provided with a compensating device for positioning the servo-valve to neutral when the signal and the position of the power cylinder piston conform to each other;

Fig. 2 is an end view of a shaft and lever arm assembly embodied in Fig. 1;

Figs. 3 and 4 are enlarged views in front and side elevation of the pneumatic signal controlled compensated hydraulic positioner and servo-valve of Fig. 1, arranged and constructed in accordance with what now appears to be a preferred form of the invention;

Fig. 5 is a detailed view in section of the pneumatic actuated positioner as embodied in the apparatus shown in Figs. 1, 3 and 4;

Fig. 6 is a view partly in section, of the hydraulic servovalve and manifold shown in Figs. 1, 3, and 4;

Fig. 7 is a view in side elevation of the servo-valve and manifold;

Figs. 8 and 9 are top and bottom plan views respectively, of the manifold; and

Fig. 10 is a top plan view of the servo-valve.

In Fig. 1 of thedtawings a power cylinder 1 is shown for operating a valve 2. Valve 2 is a large one having a large bore and stroke. The movable part of the valve is connected by a rod 3 to the piston 4 of the cylinder 1. Cylinder 1 is supplied with hydraulic fluid, such as oil, by pipes 6 and 7 connected to the bottom and top of the cylinder, respectively, as shown. The cylinder 1 being required to develop very strong operating forces, needs oil supply pressures of the order of 1500 to 2000 p. s. i. The'operation of the power cylinder 1 is controlled by a self-contained unit 8. The operation of unit 8 is controlled by a signal input pressure such as a pneumatic signal developed by a regulator (not shown) that is an indication of the position to which valve 2 must be operated in order that the medium flowing through it will be controlled to a desired order.

Unit 8 includes a pneumatic signal responsive hydraulically operated positioner 9, a servo-valve 10, and a compensating mechanism 11. The compensating mechanism 11 is operated by the movable element of power cylinder 1, namely, its piston, through a shaft 12 upon which are cranks or lever arms 13 and 14, respectively. Crank arm 13 is connected to the piston rod of the power cylinder 1 by means of a link 15 and a frame 16 carried by the piston rod 3. The frame 16 includes a cross member 17 mounted at the upper end of the piston rod 3, a cross member 18 secured to the lower end of the piston rod 3, and side bars 19 and 20 connecting the cross members 17 and 18, respectively. The crank arm 14 is connected to the compensating mechanism 11, as will be described infra.

The compensating mechanism 11 includes a compensating bar 22 having a cam follower 23 at its upper end, a cam 24 mounted on a shaft 25 and a yielding means, such as a spring 26 connected to the upper end of the lever and to an adjustable support 27 by means of which the cam follower 23 is urged against the cam 24. A crank or lever 28 is secured to the shaft 25 and is connected by a link 29 to the crank arm 14 on shaft 12.

Cam 24 is so shaped that when the piston 23 moves upwardly, the shaft 12 and its crank arms 13 and 14 are turned in such a direction that lever 28 turns in the direction of arrow 30, whereby the bar 22 and the cam follower 23 move inwardly towards the center of shaft 25 under the tension of spring 26. When the bar 22 moves in that direction, the servo-valve is moved to neutral from the position in which it supplied hydraulic fluid to the bottom of cylinder 1. If the cylinder 1 receives hydraulic fluid at the top thereof through pipe 7, piston 4 moves downwardly whereby arm 28 is moved in the direction of arrow 32, in which event the cam moves the compensating bar 22 away from the center of shaft thereby actuating the servo-valve 10 to neutral from the position in which it supplied hydraulic fluid to the top of the cylinder.

The pneumatic hydraulic positioner 9 responds to a signal, moves the compensating bar 22 about the cam follower 23 as a pivot and operates the servo-valve 10. Motion in either direction of piston 4 in the cylinder 1 results in the cam 24 returning the servo-valve to its neutral position.

The servo-valve 10 is supplied with hydraulic fluid by a pump 53 at pressures of the order of 1500 to 2000 p. s. i. from a supply tank 34. The output of the pump 33 passes through a pipe 35 to supply port 36 of the servo-valve 10. A relief valve 37 is provided in pipe 35 for returning fluid from the pipe 35 to the supply tank 34 in the event that the pressure in pipe 35 exceeds the required value, as when the ports of the servo-valve 10 are all closed.

The servo-valve is provided with an outlet port 38 that leads through pipe 7 to the upper end of cylinder 1 and an outlet port 39 that leads through pipe 6 to the bottom of cylinder 1. The servo-valve is also provided with a return port 40 that leads through a pipe 41 to the supply tank 34.

The construction of the pneumatic signal responsive hydraulic positioner 9 is illustrated in detail in Fig. 5. As there illustrated, positioner 9 comprises pneumatic signal responsive means 42, an hydraulic positioner 43 of the cylinder piston pipe, and a pilot valve 44 operated by the pneumatic signal responsive means 42.

The hydraulic positioner 43 comprises a cylinder 44 having therein a differential piston 45. The piston 45 operates in a cylindrical bore 46, one end of which is closed by a cylinder head 47. The opposite end of the bore 46 is provided with an inwardly extending annular flange 48 through which an extension 49 of the piston 45 extends. The extension 49 as shown, has a running fit with the inner surface of the annular flange 48. The flange 48 is provided with an annular groove 49 for retaining a sealing ring 50. The seal 50 may be of the O-ring type. The extension 49 is provided with an annular shoulder 51 adjacent the piston 45, the diameter of which is greater than the bore through the annular flange 48 and acts as a stop for the piston when it moves to the left as seen in Fig. 5.

The piston 45 is provided with a tubular extension 53 that passes through a bore 54 in the cylinder head 47 and terminates adjacent the signal responsive mechanism 42. The cylinder head 47 is provided with an annular groove 55 embracing the extension 53 and in which is disposed a sealing ring 57 to seal the sliding surface of the extension 53 and the bore 54. The rin 57 may be of the O-ring type.

The extension 53 and the piston 45 and its extension 49' are provided with a bore 58. In the bore portion located within the piston and its extension 49 is a bore 59 in which a ported sleeve 60 is disposed. The inner end of the bore 59 has a shoulder 61, against which the sleeve 60 abuts, the latter being yieldingly held in place by means of a compression spring 62 and a nut 63 screwed into the left hand end of the extension 49.

The sleeve 60 is provided with a supply port 64 that registers with a port 65 in the piston. The port 65 in turn registers with a supply port 66 in the cylinder 44. The sleeve is provided also with an outlet port 67 that communicates with a passage 68 leading to the space 69 adjacent the cylinder head 47.

The exterior of the sleeve 60 is provided with spaced annular flanges 70, 71, and 72 in which sealing rings 73 are retained as shown. These rings may be of the O- ring type. The flanges 70 and 71 are on opposite sides of the sleeve inlet port 64 and the flanges 71 and 72 are on opposite sides of outlet port 67, thereby segregating the supply port and the outlet ports from each other.

The pilot valve 44 operates in the bore of sleeve 60 and controls the outlet port 67. Valve 44 is provided with spaced lands 75 and 76, between which is the supply port 64. Land 75 controls the port 67. When in the position shown, that is, in neutral position, port 67 is closed. If the pilot valve is moved to the left, the space 69 in the cylinder is connected through port 67 to the supply port 66. That pressure acts on the face of the piston adjacent the cylinder head 47 and moves the piston to the left. When the piston has moved a distance suflicient for the land 75 to lap or close the outlet port 67, it comes to rest. If the pilot valve 44 is moved to the right, land 75 uncovers port 67 whereby hydraulic fluid may discharge from the space 69 through port 67 and the adjacent open end of the sleeve 60 into a discharge port 79 which leads to a drain port 80 in the cylinder 44'. When the fluid or liquid in space 69 is draining, the pressure of the supply delivered through port 66 acts on the opposite face of the piston and moves it to the right until the land 75 laps the port 67, at which time the piston comes to rest.

As shown in the drawings, the area of the face of the piston adjacent the cylinder head 47 is larger than the opposite face which is exposed to the supply pressure through port 66. Therefore, when the supply pressure acts on the face adjacent the head 47, the force acting towards the left is greater than that acting towards the right and the piston moves. When the pressure in the space 69 is relieved, the pressure on the opposite face of the piston moves it in the opposite direction. From the above, it is seen that the piston 45 always moves in the same direction that the pilot valve 44 is moved and it always comes to rest when the land 75 laps the outlet port 67.

When the outlet port 67 is closed, the piston 45 is locked against movement because the spaces on the opposite faces of the piston 45 are filled with hydraulic fluid which can not escape.

In order to seal the end of cylinder 44 through which the nut 63 projects, to prevent the escape of hydraulic fluid such as oil, that end of the cylinder is closed by a flexible member such as diaphragm 81. The marginal edge of the diaphragm 81 is clamped between the end of the cylinder 44 and a clamp ring 82 which is secured by means of bolts 83 and nuts 84.

The nut 63 has a shank 85 that extends through the central portion of the diaphragm 31 and is secured to the central portion of the diaphragm by means of a packing plate 86 and a link connecting it to .bar 22, as will be shown infra.

The supply port 66 of the body and the drain port 80 are provided with a manifold 89 (see Fig. 3). The manifold also serves the servo-valve 10 to provide a means of discharging leakage oil therefrom to a collecting reservoir.

The pneumatic signal responsive means 42 is mounted on a tubular housing 90 which butts against the cylinder head 47. The means 42 comprises a bonnet 91 and a flexible member 92, such as a diaphragm, the marginal edge of which is clamped between the bonnet and the adjacent end of the cylinder 90. The clamping is effected by the bolts 83 and nuts 93., The bolts 83 as shown secure the entire assembly together as a compact unit.

The central portion of the diaphragm 92 is supported by an inverted cup-shaped member 94 and is clamped thereto by a backing plate 95 and screws 96. The bonnet 91 is provided with a tubular extension 97 in which is housed a relatively light compression spring 98. The spring is engaged by an adjusting nut 99 which has screw thread engagement with the interior of the extension 97.

The outer end of the extension 97 is closed and sealed by a threaded plug 100. The spring 98 as shown bears on the backing plate 95. The connection of the diaphragm 92 to the pilot valve 44 is made through the backing member 95. As shown, the central portion of the backmg member is provided with a screw 101 which is locked in place by a lock nut 102. The inner end of the screw 101 is provided with a V-shaped bearing or way 103, a threaded nut 104, and a link 105. The link 105 has a knife edge 106 that is received in the way 103. The opposite end of the link 105 is provided with a knife edge 107 that is received in a way or bearing 108. The way 108 is formed at the end of the pilot valve 44 and is provided with a threaded portion 109 and a stop or bearing collar 110.

The link 105 is held in engagement with the ways 103 and 108 by means of a coil spring 111, the ends of which are threaded on the portions 94 and 109, respectively. The tension in the spring 111 may be adjusted by turning the nut 102.

The bonnet 91 is supplied by pneumatic signal pressure through a port 112. The pressure acting on the diaphragm 92 is resisted by a spring 113. Therefore, for each value of pressure supplied to and acting on the diaphragm 92, there will be a definite amount of deflection in spring 113 and a definite amount of linear motion imparted to the pilot valve 44. Increasing pressures supplied to bonnet 91 move the pilot valve 44 to the left, as seen in Fig. 5, while decreasing pressures result in motion to the night, that motion being effected by the spring 113. In the event the oil should leak past the ring 57 into the tubular member or support 90, provision is made for draining that oil by providing the cylinder head 47 with a drain port 115 leading to a passage 116 that is connected to the manifold 89 of Fig. 3.

As shown in Fig. 3, the device 9 is mounted in a case or cabinet 117 at the bottom thereof. The device 109 is secured rigidly in place in the case by means of bolts 118 that pass through the case into the manifold 89 and cylinder 44. Access to the plug 100 and the adjusting nut 99 may be had through an opening 120 in the side of the case.

The nut 63 of the positioner is connected to the compensating bar 22 by means of a link 121 one end of which is threaded on stem 63 against plate 86. The link 121, as shown in Fig. 3, passes between a bifurcation in the adjacent end of the bar 22 and .is pivoted thereto by a pin 122.- The bifurcation .is formed by the end of the bar and a bent plate 123 which is secured with bolts 124 to the bar. The end of link 121 adjacent the case is provided with a slide bearing 125 that is received in a sleeve 126 of a bearing member 127 that is secured to the case with screws 128. The slide bearing 125 and 126 supports bar 22 and maintains it in alignment with the piston of the positioner 9.

The servo-valve comprises a valve body 129 and a manifold 130. The valve and manifold are illustrated in Fig. 3 and the Pigs. 6-10 inclusive.

The valve body 129 is provided with a bore 131 in which is a sleeve 132. The sleeve is provided with a supply port 133, outlet ports 134 and 135 and drain or return ports 136 and 137, the latter being adjacent the opposite ends of the sleeve. The 'Valve body is provided with annular undercut grooves 138, 139, and 140 that register with ports 133, 134, and 135, respectively. The body is also provided with annular grooves 141 and 142 that register with the ports 136 and 137, respectively. The grooves 141 and 142 register with a common passageway 143 located above the ports 133, 134, and 135 to provide the drain or return way of the valve. The sleeve 132 is provided with a plurality of spaced annular grooves 144-149 inclusive, in which are retained sealing rings 150 such as 0 rings, for example. The rings 150 being located as shown, seal the respective ports 133, 134, 135, 136, and 137 from one another.

A valve member 151 is slidably disposed in the sleeve 132. Member 151 is provided with spaced lands 152, 153, which control the outlet ports 134 and 135, respectively, and lands 154 and 155, which are located outwardly of the outlet ports 136 and 137, respectively. The valve body 129 and the manifold are provided with registering passageways and ports, as can be seen by inspection of Figs. 6 and 8. As shown in Fig. 6, the manifold is provided with the ports 36, 38 and 39 that are drilled from the side of the manifold in a horizontal direction, parallel to each other. The manifold is bored vertically to provide passageways 163, 164 and 165 that communicate with the horizontal ports 36, 39, and 38, respectively. Port 36 is provided with internal pipe threads 166 to accommodate the supply pipe 35 of Fig. 1. Similarly, ports 39 and 38 are internally threaded as at 167 and 168, to accommodate the pipes 6 and 7 of Fig. 1, these pipes supplying the power cylinder 1. As may be seen in Fig. 8, the vertical passageway 163 connecting with port 36 is towards the front of the manifold and communicates with the annular groove 138 by which port 133 of the sleeve 132 is supplied. It may also be seen in'Fig. 8 that the vertical passageways 164 and 165 are located towards the rear of the manifold and communicate with the annular grooves 139 and 140 that supply the outlet ports 134 and of the sleeve 132. The return port 40 is provided with internal threads 171 for accommodating the return or discharge pipe 41 of Fig. 1. A vertical passageway 172 connects port 40 with the return passage 143 of the'valve body. Thus the fluid discharging from the ports 136 and 137 flows up passageway 172, port 40 and pipe 41 to the supply tank 34.

The outlet ports 139 and extend rearwardly of the valve member 151, while the supply port 138 extends forwardly thereof. The return or discharge port 40 and the passage 143 are directly above the center of the valve body bore 131.

To cause piston 4 to move upwardly, valve member 151 is moved to the left of neutral (Fig. 6). In that position, supply port 133 is connected to outlet port 134 which leads to pipe 6 and the bottom of cylinder 1 of Fig. 1. At the same time the top of the cylinder is connected to drain through pipe 7, port 38, the passageway 165, the outlet port 135, dis-charge passageway 172, port 40 and pipe 41 to tank 34. To move piston 4 upwardly, valve 151 is moved to the right of neutral position. In that position port 133 is connected by port 135 and passageway to the outlet port 38 to the top of the cylinder 1. As the upper end of the cylinder is connected to discharge through port 39, passage 164, ports 134 and 136, and passages 143 and 172 to the return pipe 41, the liquid on the lower side of the piston is expelled as the down stroke progresses.

One end of valve member 151 is provided with a socket 173 into which a tubular sleeve 175 extends. The sleeve is connected by a pivot pin 176 to the socket. The outer end of the sleeve is internally threaded to accommodate an eye-bolt 177 by means of which the valve member 151 may be connected to the-compensating bar 122. I

In order to prevent escape to the atmosphere of such oil as may leak past lands 154 and 155, the ends of the bore 131 in the valve body are closed by caps-178 and 179. As shown, the cap 1'78 is provided with a gasket 180 so that when the cap is secured firmly to the valve body with screws 181, an oil-tight joint is formed at the end of the bore and the sleeve 132.

The cap 179 comprises an annular ring 182 having a diaphragm 183 extending across the same. The marginal edge of the diaphragm is clamped between the outer end of the annular ring 182 and a ring 184. The clamping is effected by screws 185 which secure the rings 184 and 182 to the valve body 129. The central portion of the diaphragm 183 is clamped between a ferrule 187 and a backing "plate 188- which, is pulled up tightly against the ferrule by means of a nut 189 threaded on the eyebolt 177. The eye-bolt 177 accommodates a pivot pin 190 that extends through the bifurcated end of a link 191 and the eye of the bolt 177 as shown in Fig. 3. The link 191 is connected to the compensating bar 22 by means of an eye-bolt 192 that is adjustably threaded into a threaded member 193, which, in turn, is threaded into the link 191 and locked in adjusted position by means of a nut 194. The member 192 may be turned into or out of the member 193 and locked in adjusted position by means of lock nuts 195 and 196.

The valve body 129 is secured to the manifold by means of stud bolts passing upwardly from the bottom of the body into the lower end of the manifold. The locations of these bolts are indicated in Fig. 9 and are identified by numerals 198, 199, 200, 201. and 202.

As may be seen in Fig. 6, the bottoms of the passageways 163, 164, 165, and 172 are provided with countersunk recesses 202-205 inclusive, which accommodate sealing rings 206. These rings may be of the O-ring type. As shown in Fig. 6, also, the passageway leading from port 136 to passage 143 is provided with a seal ring 207 upon which the bottom of the manifold rests to block off the top of that opening. Thus, when the stud bolts are drawn up tightly, the body 129 is pulled up tightly against the bottom of the manifold and the seals to provide a fluid-tight joint therebetween.

As shown in Figs. 3 and 4, the cam shaft 25 is supported in a bushing 208 having a fiange 209. A portion of the bushing 208 extends outwardly through the back 210 of the case 117. The collar or flange 209 abuts the back and is secured to it by means of bolts 211 and nuts 212. In order to limit endwise movement of the shaft 25 it is provided with a collar 213 at its outer end to which it is secured by means of a set screw 214.

The inner end of shaft 25 carries the cam 24. The cam 24 is provided with a hub 215 that is keyed to the shaft by means of set screws 216. The cam follower 23 is mounted on a pin 217 that extends through a bushing 218. The pin is secured to the bar 22 by means of a nut 219. To limit the travel of the cam 24 in a counterclockwise direction, as seen in Fig. 3, an angle member 221 is secured to the back of the case 117.

The cam actuating lever 28 is mounted on the Outer end of the shaft 25 and is secured thereto by a set screw 223.

In the event that it is desirable to provide means for indicating the position of the piston 4 of power cylinder 1, a potentiometer 225 may be employed for supplying potential to an indicating meter (not shown).

The potentiometer includes a gear wheel 226 mounted on the camshaft 25 and which is provided with a. potentiometer resistance 227. The potentiometer resistance co-operates with a contact-carrying plate 228 mounted on a support 229 which, in turn, is supported by bolts 230 which pass through tubular spacers 231, the bolts 230 passing through the back of the case 117. The contact plate member 228 has three leads 232, 233, and 234 that lead to a terminal block 235. The center lead 232 would correspond to the neutral or central position of the mechanism shown in Fig. 3 and to the mid-position of the piston in cylinder 1.

The side of the case 117 is provided with a fitting 236 to which is connected a T 237, provided with a gauge 238. The fitting 237 is connected to a supply pipe 239 that leads to the inlet port 66 of the body 49 of the valve positioner 9. The fitting 236 would be connected to a supply of hydraulic pressure of the order of, say, 200 p.s. i.

The side of the case 117 is also provided with a fitting 240 that is connected to a T 241 having a gauge 242 for indicating the pressure of the pneumatic signal supplied to the fitting 240. The T 241 is connected to a pipe 243 to the port 113 of the pneumatic signal-receiving means 42 (see Fig.

The leakage of oil past the ends of the servo-valve 8 into the caps 178 and 179 is carried by pipes 244 and 245, respectively, into the manifold 89, from which it is drained 'by a pipe 245' into a gravity flow T 247. While not shown, it is to be understood that the T 247 would be connected to a line leading back to the supply tank 34 or other collector.

From the foregoing description it is seen that the pneumatic signal-receiving hydraulic positioner 9 the servovalve 10 and the compensating mechanism are all contained within a compact, relatively small case 117 and that the movable element, such as piston 4, which is to be controlled thereby, may be close to or relatively remote from the unit 8.

When unit 8 is to be adjusted for operation, the piston in cylinder 1 is moved to mid-position. The cam lever 28 is adjusted to mid-position so that the cam 21 will be in midposition. Next, the valve link 191 is adjusted for length so that the valve element 151 will be in neutral position. Likewise, the link 121 which connects the piston of the positioner 9 to the bar 22 is adjusted to mid-position, and the pilot valve 44 to neutral position. All these adjustments are made for a signal pressure to the means 42 corresponding to the mid-range of pressure signals to be supplied thereto. When positioner 9 has been so adjusted, the piston thereof will be in the midrange position and the pilot valve 44 will be neutral.

To prevent overtravel of the compensating bar 22, a plate 250 is provided, having a forwardly projecting flange 251 in which is a notch 252. The sides of the notch are so spaced from the bar 22 that when it is in neutral position, they will be equidistant from the edges of the bar.

Assuming now that the signal pressure received by the responsive means 22 increases above the mid value of the signal, which may be 30 pounds gauge pressure, the pilot 44 is moved to the left, uncovering the port 67 so that pressure, that is, oil or liquid pressure, is supplied to the space 69 of the cylinder 44. That pressure will move the piston 45 to the left until the port 67 is lapped by the land 75 at which time the piston 45 comes to rest. Movement of the piston 45 in that direction moves the compensating bar 22 clockwise about the cam follower pin 217 as a pivot; therefore, the movable valve member 151 of the servo-valve is moved to the left, whereby hydraulic pressure is admitted into port 134, passageway 164, and port 39 to pipe 6 which leads to the lower end of the cylinder 1. At the same time, the upper end of the cylinder is connected to drain, as previously explained, so that the piston 4 will move upwardly. As the piston moves upwardly, the cam 24 is turned counter-clockwise, which results in the bar 22 being turned clockwise by spring 26 about the pivot pin 122. That movement of the bar 22 results in the valve member 151 being returned to neutral position and arresting movement of the piston 4. If the pressure signal decreases, the pilot valve 44 is moved to the right, whereby the pressure on the larger face of the piston of positioner 9 is relieved, causing the piston to move to the right whereby the valve member 151 is moved by the bar 22 to the right and hydraulic pressure is admitted to the top side of the piston 4 through the passageways described, supra, causing the piston to move downwardly. As the piston moves downwardly, the cam 24 is turned clockwise, and the bar 22 is turned counterclockwise about the pivot 122 thereby returning the valve member 151 of the servo-valve to neutral position and again arresting motion of the piston 4. Thus the piston 4 will move in incremental steps with each increment of change in the signal pressure above or below the neutral value.

Having thus described the invention, it will be apparcut to those of ordinary skill in this art, that various modifications and changes may be made in the illustrated embodiment without departing from either the spirit or the scope of the invention.

Therefore, what "is claimedas new anddesired to be secured by Letters Patent is: v t

1. A pneumatic signal responsive hydraulic actuated positioner comprising a cylinder and a cylinder head at one end thereof, the cylinder having a bore therein, a differential piston in the cylinder bore, one face of which is larger in area than the other, a central bore in the piston coaxial with said cylinder bore, a sleeve in the piston bore, said sleeve having an inlet port for hydraulic fluid and an outlet port, the piston having a port therein communicating with the sleeve outlet port and with that end of the cylinder to which the piston face of larger area is exposed, the cylinder having a supply port for supplying hydraulic fluid to the piston face of smaller area, a pilot valve in the bore of the sleeve and provided with spaced lands disposed on either side of the sleeve inlet port, one of said lands controlling the outlet port of said sleeve, and means connected to said pilot valve for actuating the same in response to a pneumatic signal force being applied thereto, the piston moving in the same direction as the pilot valve and coming to rest when the outlet port of the sleeve registers with its controlling land, the outlet port in said sleeve also communicating with the discharge end of the cylinder bore when the controlling land shuts off communication between the supply port and the outlet port.

2. A pneumatic signal-responsive hydraulically actuated positioner comprising a cylinder which is closed at one end by a cylinder head and at the opposite end by a flexible member, a differential piston in the cylinder, the piston face adjacent the cylinder head being of larger area than the opposed face thereof, the piston having a coaxial bore therein which is open to the end of the cylinder adjacent said flexible closure member, the cylinder having a supply port for hydraulic fluid and another port communicating with the bore of the piston and leading to the cylinder head end of the cylinder, a sleeve in the piston bore, said sleeve having a port communicating with the cylinder supply port and the port communicating with the ports leading to the cylinder head end of the cylinder, a pilot valve disposed in said sleeve and having spaced lands between which the supply port of the sleeve is disposed, one of said lands controlling the outlet port of the sleeve and, when in one position, directing fluid to the cylinder head end of the cylinder and, when in another position, connecting that space to drain, the piston being provided with a shoulder for limiting the stroke in one direction, movement of the head of the piston with the larger face being limited by the cylinder head when moving towards it, and a pneumatic operator for actuating the pilot valve comprising a pressure tight housing having a pressure-deflectable member provided with a link connected to the pilot valve, said pressu-re-defiectable member being provided with a compression spring against which the deflectable member works in response to increasing pneumatic pressures being supplied to said housing, the device being characterized by the fact that when the pressure on the pressure-deflectable member increases, the pilot valve stem is actuated in a direction to supply hydraulic fluid to the cylinder head end of the cylinder, whereby the piston moves in the same direction as the pilot valve stem until a position is reached where the controlling land of the pilot valve closes the outlet port of the sleeve, and that the characteristics of the spring which opposes deflection of the pressure-deflectable member causes the diaphragm to come to a fixed but different position with each value of pressure applied thereto, the diaphragm being urged in the opposite direction by the spring on decreasing signal pressures whereby the pilot valve is actuated in the opposite direction to connect the cylinder head end of the cylinder to drain, thereby causing the supply pressure to act on the smaller area of the piston and move it in the same direction as the pilot valve moves until the outlet port of the sleeve is closed by the controlling land of said pilot valve.

3. A mechanism as in claim 2, in which the end of the cylinder opposite the tubular extension of the piston is provided with a flexible closure member, that the central portion of the closure member is provided with means for connecting the same to the piston and to a member to be positioned thereby.

4. A servo-valve comprising a valve body having an open-ended bore, a supply port, outlet ports, one on each side of the supply port, and a discharge port for each outlet port, a sleeve in the bore provided with spaced ports registering with the respective body ports, a movable valve member on said sleeve provided with spaced lands, there being a land on each side of the supply port and so located as to close the outlet ports when the valve member is in neutral position, there being lands on each side of the outlet ports, said movable valve member when out of neutral position connecting one of said outlet ports to the supply port and the other outlet port to its discharge port, a cap secured to said body to close one end of the body bore, and a cap over the opposite end of the bore, said latter cap including a flexible diaphragm, means extending through said diaphragm and connected to one end of the movable valve member for actuating the same, said caps having drain ports through which hydraulic fluid that leaks past the ends of the valve member may escape.

5. A servo-valve as in claim 4 which is provided with a manifold adapted to be secured to the valve body, the manifold having spaced outlet ports to which outlet piping may be connected, each outlet port being provided with a passage registering with the respective outlet ports in the valve body, a supply port provided with a passage registering with the supply port of said valve body and a return port provided with a passage communicating with the discharge ports of said valve body.

6. A pneumatic signal responsive hydraulic actuated positioner comprising a cylinder and a cylinder head at one end thereof, the cylinder having "a bore therein, a differential piston in the cylinder bore, one face of which is larger in area than the other, a hollow tubular extension projecting from the piston face of larger area through said cylinder head, a central bore in the piston coaxial with said extension, a sleeve in "the piston bore, said sleeve having an inlet port for hydraulic fluid and an outlet port, the piston having a port therein communieating with the sleeve outlet port and with that end of the cylinder to which the piston face of larger area is exposed, the cylinder having a supply port for supplying hydraulic fluid to the piston face of smaller area, a pilot valve in the bore of the sleeve and provided with spaced lands disposed on either side of the sleeve inlet port, one of said lands controlling the outlet port of said sleeve, a pressure-tight housing on the cylinder head end of the cylinder and provided with a pressure-deflectable member, the pressure-deflectable member being connected to said pilot valve stem, and means yieldingly opposing movement of the deflectable member in response to increasing pneumatic pressures being applied thereto, the piston moving in the same direction as the pilot valve and coming to rest when the outlet port of the sleeve registers with its controlling land, the outlet port in said sleeve also communicating with the discharge end of the cylinder bore when the controlling land shuts olf communication between the supply port and the outlet port.

7. A device as in claim 6 in which the piston is provided with a hollow tubular extension that extends through the cylinder head and that the link connecting the pressure-deflectable member with the pilot valve is disposed within the tubular extension, and that the sleeve in the bore of the piston is urged to a seated position by yielding means within the piston.

8. A device according to claim 6, in which the cylinder is provided with an inwardly extending annular 11 groove containing a yieldable sealing ring that engages to piston wall to seal the same.

9. A device according to claim 6, in which theeylinder head through which the tubular extension of the piston extends is provided with an under cut annular 5 groove embracing the tubular extension and in which groove is a yieldable annular sealing member that engages the walls of the tubular extension.

UNITED STATES PATENTS Smoot Aug. 5, 1930 Mitereflf Nov. 12, 1935 Ring et a1. Jan. 25, 1938 Kniskern Nov. 15, 1938 Ziebolz Dec. 31, 1940 

